Cytokine-mediated inhibition of astrocyte gap junction coupling as a cause of temporal lobe epilepsy

颞叶癫痫（TLE）是成人癫痫最常见的形式。目前的治疗方法只能抑制癫痫发作，但不能治愈该疾病，并且对超过 2/3 的患者无效。因此，迫切需要新的治疗策略和靶点。在这方面，星形胶质细胞近年来引起了越来越多的关注，因为已经清楚它们积极调节神经元兴奋性和突触传递。我们之前已经表明，星形胶质细胞之间的间隙连接耦合在神经元高活动期间增强的细胞外 K 和谷氨酸水平的缓冲中起着关键作用，在实验性 TLE 开始后迅速受损，并且在患者和动物模型的疾病慢性期中完全不存在。我们最近的数据表明星形胶质细胞解偶联是由促炎细胞因子 TNFα 的可溶形式介导的。值得注意的是，可溶性 TNFα 的特异性抑制不仅可以防止癫痫引起的解偶联，而且在我们的动物模型中产生了显着的抗癫痫和抗癫痫发生作用。因此，我们假设在最初的致癫痫事件后小胶质细胞 TNFα 的释放触发了星形胶质细胞间隙连接耦合的破坏，这反过来在 TLE 的发生和进展中发挥着关键作用。为了检验这一假设，在本申请中，我们将 i) 揭示实验性 TLE 中细胞因子表达和星形胶质细胞解偶联的时间过程，ii) 测试 TNFα 的小胶质细胞起源并确定其对星形胶质细胞功能影响的分子机制，以及 iii) 证明 TNFα 诱导的星形胶质细胞解偶联作为 TLE 原因的关键作用。该项目将增进我们对癫痫发生机制的理解，并阐明针对​​神经胶质信号传导途径开发新的、改善疾病的治疗策略的潜力。

Temporal lobe epilepsy (TLE) is the most common form of adult epilepsies. Current treatments only suppress seizures but do not cure the disorder, and are inefficient in more than 2/3 of the patients. Hence, new therapeutic strategies and targets are urgently needed. In this regard, astrocytes have attracted increasing attention during recent years, since it has become clear that they actively regulate neuronal excitability and synaptic transmission. We have previously shown that gap junction coupling between astrocytes, which plays a key role in buffering of enhanced extracellular K+ and glutamate levels during high neuronal activity, is rapidly impaired after initiation of experimental TLE, and completely absent in the chronic phase of the disease in both, patients and an animal model. Our recent data suggest that astrocyte uncoupling is mediated by the soluble form of the proinflammatory cytokine, TNFα. Remarkably, specific inhibition of soluble TNFα not only prevented seizure-induced uncoupling but also yielded significant antiepileptic and antiepileptogenic effects in our animal model. Thus, we hypothesize that release of microglial TNFα after an initial epileptogenic event triggers disruption of astrocytic gap junction coupling, which in turn plays a key role in the development and progression of TLE. To test this hypothesis, in the present application we will i) unravel the time course of cytokine expression and astrocyte uncoupling in experimental TLE, ii) test the microglial origin of TNFα and identify the molecular mechanism(s) of its influence on astrocyte functions, and iii) prove the crucial role of TNFα-induced astrocyte uncoupling as a cause of TLE. This project will increase our understanding of the mechanisms of epileptogenesis and elucidate the potential of targeting glial signaling pathways for developing new, disease-modifying therapeutic strategies.